This invention relates generally to antennas and more particularly to horn antennas.
In many radio frequency systems, limited space is available for antennas. Antennas designed for small spaces, however, must meet various performance requirements. For example, the antenna must have a specified angular coverage and frequency bandwidth. Thus, existing antennas may not meet both the size and performance requirements in a system.
One common size constraint in airborne systems is that the antenna not protrude beyond the aircraft carrying the RF system. Thus, a "flush mount" antenna is required.
Various forms of flush mount antennas are known. For example, annular slot antennas, cavity inductors, strip inductors, patch antennas, surface-wave antennas and slot antennas can all be mounted flush with a surface. However, these types of antennas generally have narrow frequency bandwidths. They are thus not well suited for systems requiring frequency bandwidths of 3:1. Printed log-periodic dipoles can be cavity backed and flush mounted. These antennas can be built with 3:1 frequency bandwidths, but cannot be made small enough to meet the size constraints of some applications.